And that is equal to the change in electric flux over time, multiplied by the permittivity of free space constant.
这等于电通量随时间的变化乘以自由空间常数的介电常数。
英语百科
Length constant
（重定向自Space Constant）
In neurobiology, the length constant (λ) is a mathematical constant used to quantify the distance that a graded electric potential will travel along a neurite via passive electrical conduction. The greater the value of the length constant, the farther the potential will travel. A large length constant can contribute to spatial summation—the electrical addition of one potential with potentials from adjacent areas of the cell.